This invention relates to a cardiac valvular prosthesis which is used as a substitute for diseased cardiac valves. The cardiac valvular prosthesis of this invention can also be used in an artificial heart, presently in experimentation, and also in "valvular conduits" that can be used in the correction of congenital cardiac diseases.
At present, there are many cardiac prostheses in existence, Many of them are in industrial production, and others are in the experimental phase. Nevertheless, until now, all of the prostheses that have been used have presented various inconveniences of different degrees, of which the most important are the following:
1. Insufficient disc opening. This occurs with a prior art valve known as the Bjork-Shiley's valve, whose design prevents an opening of more than 60.degree.. This causes the appearance of high pressure gradients throughout the valve which is especially severe in small sizes, causing the heart to overwork itself, thus preventing the use of this valve in extreme cases. This also creates an unfavorable hydrodynamic situation in the minor segment of the valve hole which, because of its small size, only permits a reduced flow through it, which is far slower than that of the major segment, thus producing blood stagnation. This is not the case with the cardiac valvular prosthesis of the present invention, since the inventive valve has a complete opening and there are no significative differences in the blood stream between the two disc segments and the gradients are minimal. Therefore, the overworking of the heart with the valve of the present invention is almost nil.
2. Production of turbulence. The majority of the mechanical valves in existence, at present (Bjork-Shiley, and others such as Omniscience, St. Jude, Starr-Edwards, et.), produce severe turbulence caused, in part, by deficient disc opening, which never reaches 90.degree. in any of the models, because of their form and joining systems. The complete opening and the hydrodynamic design of the disc or occluder in the valve of the present invention avoids this problem.
3. Tendency to thrombosis. All mechanical valves tend to produce thrombosis. The prosthesis of the present invention attempts to reduce this problem to a minimum. A production factor of thrombosis is turbulence. The type of hinges of the occluder with the supporting ring and the location site of these hinges are also important. In general, many of the present valves (St. Jude, Omniscience, Kaster-Lillehey) have their hinges in the disc's periphery, making contact with the inside of the supporting ring. This is a serious inconvenience, as this zone has zero flow, according to Newton's Law of Fluids, thus having a tendency to cause stagnation and thrombosis. One way of reducing thrombosis in the hinges of the disc with the ring, would be to situate these hinges in the central area of the disc where, according to the mentioned Newton's Law of Fluids, the current is of maximal intensity.
4. Non-hydrodynamic designs of the disc and unfavorable position when open. It is believed that the mechanical valves in existence, at present, have not sufficiently taken into consideration the hydrodynamic factors when designing the obturator discs, which is considered to be essential in the avoidance of turbulence and thrombosis. Also erroneous in the prior art valves is the oblique position of the disc when fully open.
5. Flat design of the ring in the aortic valves. All of the mechanical cardiac valves in use, present a flat implantation ring. This is adequate when they are used in mitral or tricuspid positions, because the cardiac annuluses of these valves are flat too; but it is very inconvenient when the valve is an aortic one, because the aortic annulus of the patient has a scalloped shape.
The valve of the present invention, solves this problem, with a scalloped implantation ring which can be fully adapted to the annulus of the patient. This not only reduces tension in the suture line, but it protects the coronary ostium and allows the implantation of a larger sized valve, reducing the transvalvular gradients.
6. Poorly-washed hinges. As it has been noted above, the hinge zone between the ring and the obturator is very prone to produce thrombos. Therefore, it is necessary to design this area in such a way so that the function of the valve guarantees the washing-out of the hinges. In the present invention the hinges are located in the rapid flow area. Furthermore, there are no profound holes or orifices that may produce stagnation of the blood, and the joint cavity is flat, superficial, large and totally open. An oblique surface precedes the hinge area, and this canalizes the blood flow towards the hinge during opening and closing, inversely to the advancing of the contact line of the hinge with the joining part of the disc. This condition guarantees a proper washing-out of the joining surface.